This application claims the priority of German application No. 196 24 883.3 and PCT/EP97/03126, filed Jun. 21, 1996 and Jun. 16, 1997, respectively, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a battery which during maintenance or danger can be easily and safely converted from an operative status to an inactive status thereby avoiding short-circuiting.
Batteries and battery systems are becoming increasingly important for primary and secondary power supply purposes. This increasing importance is in part due to the ever increasing demands in connection with the environmental compatibility of power supply systems in the sense of emission protection and reusability or recyclability of raw materials and energy.
This primarily applies to the final consumer and consequently private households. But also applies to public installations, more particularly with regards to infrastructure and affix which is being equipped with more environmentally compatible power sources.
Mobile equipment, such as e.g. road vehicles and also rail vehicles and watercraft are already being equipped with environmentally friendly and reusable or rechargeable power sources in the form of accumulators or batteries. In addition, ever greater use is being made of such power sources in the form of battery systems in stationary installations, such as e.g. standalone devices or as emergency power sources in buildings.
In general, with all power sources and power supply means, the problem exists that the release of power is desirable in the normal operating state, but in the case of an accident, danger or damage, or also in the case of maintenance work, it is necessary to achieve a very fast and clearly defined disconnection of the power source or power supply.
For example, in the case of internal combustion engines the battery is transferred from an operative state into an inoperative state by switching off the ignition and by interrupting the fuel supply the engine. Thereafter no power is released, apart from any residual heat. However, in the case of batteries or battery systems the difficulty exists that even after the separation or interruption of the supplying leads, the battery or battery system still generates power. There is still the terminal voltage at the battery or battery system terminals in the form of the no load or open-circuit voltage of the battery.
Thus, in the case of an electric car, if an accident occurs, an emergency cutout reacting to the impact interrupts all leads to the power supply. However, due to the deformation of the vehicle on impact an electric contact may be formed between the battery terminals and conductive parts of the vehicle, particularly the vehicle body. As such, there is a risk of an electric shock for persons hurrying to recover the wreck or assist the occupants.
In addition, by deformation of the battery compartment even the battery can be short circuited. As a result, in certain circumstances, considerable current may still flow, accompanied by sparking. There is a considerable fire risk at the accident location, which can lead to a great increase in dangers and risks for objects or persons.
Therefore an object of the invention is to provide a battery which, for maintenance purposes or in the case of a hazard, can be simply and reliably transferred from an operative state to a safe inoperative state, while avoiding a battery short circuit.
The object of the present is achieved in that a battery is created having at least one controlled operable rapid draining device. This rapid draining device is used for the rapid draining of the electrolyte from the electrolyte compartment. According to this solution, following the draining of the electrolyte, the electrodes remain completely or substantially unwetted by the electrolyte. As such, the electrodes are galvanically isolated from one another.
Compared with the prior art, these inventive measures have the advantage that in the case of a danger or maintenance situation, the battery can be transferred in a controlled and clearly defined manner into a safe, inoperative state. After draining the electrolyte and consequently after the galvanic interruption of the electrode connection, all the current-generating, electrochemical processes of the battery are interrupted. Even if the battery compartment is deformed and the battery terminals come into contact with any conductive areas, no electric shock hazard exists, because in this inoperative state the battery cannot generate electricity.
In the simplest case the electrolyte simply flows out of the electrolyte compartment. However, for environmental compatibility and electrolyte reusability reasons, it is appropriate to provide at least one electrolyte collecting tank for receiving at least part of the electrolyte from the electrolyte compartment. The electrolyte can be safely drained so that the environment is not contaminated. In addition, following the elimination of the hazard or at the end of the maintenance work, the electrolyte can be returned to the electrolyte compartment to reactivate the battery.
A particularly preferred battery system with a high battery capacity is obtained if the electrolyte compartment has a reaction compartment with electrodes and a reservoir communicating with the reaction compartment for receiving a larger electrolyte supply. It is particularly advantageous for the reaction chamber to have a small volume compared with the reservoir. The small reaction chamber is then faced by a very large electrolyte reservoir, so that the battery system acquires a particularly large capacity, which greatly increases the travel range for electric vehicles. In addition, compact and/or non-porous electrodes are advantageous.
Communication between the reaction chamber and the reservoir is advantageously provided by an exchange line. In a particularly simple manner of use, convection, which is produced as a result of the density difference between the used and unused electrolyte is used. In order to increase convection and therefore the electrolyte exchange between reaction chamber and reservoir, there is at least one pump or a stirring, circulating or heating device. This device can be positioned either in the exchange line, in the reaction compartment or in the reservoir.
A particularly simple draining of the electrolyte from the electrolyte compartment into the electrolyte collecting tank is achieved if the electrolyte collecting tank is arranged substantially below the electrolyte compartment. Gravity then spontaneously drives the electrolyte downwards into the electrolyte collecting tank. It is advantageous to provide an electrically controllable closing or sealing device in the rapid draining device for the rapid draining of the electrolyte. This prevents electrolyte flow between the electrolyte compartment and the electrolyte collecting tank, in particular the draining of the electrolyte in at least one direction. This prevents an outflow of electrolyte in the normal operating state and ensures that when the electrolyte has been drained there can be no return flow of electrolyte from the electrolyte collecting tank into the electrolyte compartment and consequently there can be no reactivation of the battery.
This closing device is advantageously constructed as on baised valve held open in the currentless state. In the normal battery operating state the open valve in the currentless state is supplied with a current and therefore kept closed. In a danger situation the current flow is interrupted in a controllable manner, so that the valve opens and the electrolyte is drained from the electrolyte compartment into the electrolyte collecting tank, deactivating the battery. Particularly simple disposable closing devices are obtained if the closing device of the rapid draining line is constructed as an explosive bolt, a preset breaking point, etc.
A further advantageous construction of the battery according to the invention is obtained by the provision of a line for delivering electrolyte between the electrolyte collecting tank and the electrolyte compartment in at least one direction. Then, following the end of the danger situation or maintenance work, the drained electrolyte can be conveyed back from the electrolyte collecting tank into the electrolyte compartment for reactivating the battery.
A further advantageous development results from the construction of at least one controlled operable delivery device for delivering the electrolyte between the electrolyte collecting tank and the electrolyte compartment. This speeds up and assists the draining of electrolyte from the electrolyte compartment. This is particularly advantageous if the electrolyte collecting tank is positioned above the electrolyte compartment or if, as a result of a danger situation, the battery system is upside down due to the accident (vehicle turned over). A controlled operable delivery device of this type can also be used for returning the drained electrolyte from the electrolyte collecting tank into the electrolyte compartment.
Such a delivery device can be for example a pump, electrically operated pump. Advantageously, the delivery device may be formed of a device for the expulsion or removal of the electrolyte from the electrolyte compartment. If said expulsion device is constructed as a gas pressure cartridge, there is a particularly rapid expulsion of the electrolyte from the electrolyte compartment and consequently a further reduction in the accident risk as a result of electric shock.
A further simplification is obtained by the construction of the rapid draining device as an emergency drain opening. Alternatively, the device may be a riser or U-tube with closure parts. Emphasis is placed on the rapid draining of the electrolyte from the electrolyte compartment.
According to another embodiment the invention, the object is also achieved by a battery provided with at least one deactivating compartment separate from the electrolyte compartment and which receives a deactivating substance. In this embodiment, there is a line for connecting the electrolyte compartment to a deactivating compartment. There is also a delivery device for the controlled transfer of the deactivating substance from the deactivating compartment into the electrolyte compartment. The deactivating substance is chosen in such a way that it prevents, deactivates or at least limits to a safe level all current-generating electrochemical or electrolytic processes in the electrolyte compartment.
Also in the case of this embodiment according to the invention, the prior art problem, that following damage, the power source still carries latent energy, is addressed in that the actual power or energy-supplying process is stopped. In this case this is brought about by the power-generating processes being suppressed by adding a substance to the electrolyte.
The deactivating substance can be in the form of a powder to be shot in, or as a liquid or a gas. If the deactivating substance in the deactivating compartment is under pressure, the delivery device can be constituted by a valve, which is in open in the currentless state, so that on disconnecting the power supply it opens in a danger or maintenance situation. Independently thereof or in addition thereto, the delivery device can also be a pump, which is in particular electrically controlled and operates electrically.
It is advantageous for the line to carry a check valve for preventing a return flow of the deactivated electrolyte into the deactivating compartment.
The electrolyte is advantageously constituted by an electrolyte comprising or in combination with H2SO4 or KOH or an organic electrolyte. Correspondingly, the deactivating substances are dilute lyes, particularly KOH, NaOH, etc. or saline suspensions, particularly milk of lime, etc. or powders, particularly of CaCO3, oxides, etc. or their suspensions or dilute mineral acids, carbon dioxide, organic acids, particularly citric acid or the like, saline suspensions, particularly FeCl3, etc. or powders of acid anhydrides or their suspensions or oxidizing or precipitating agents.
In all these batteries or battery systems according to the invention, it is particularly advantageous to provide a control device for controlling the delivery devices and/or valve means using control lines. This permits a clearly defined disconnection in the case of danger or maintenance.
A particularly easily handleable battery or battery system is obtained if the control device is designed for detecting a signal of a danger situation and/or a user activation. When the signal is detected the, draining of the electrolyte or the deactivation of the electrolyte can be initiated. The control device advantageously has at least one sensor means, which can be designed as an acceleration sensor or as a manually operable emergency cutout.